Numerous machines have been devised for forming fold-down preglued boxes from preformed blanks. However, most of these prior machines have automatically performed all of the folding and glueing steps, and particularly have automatically folded both the front and rear corner tabs prior to glueing thereof to the side flaps. These machines have thus been unduly complex, both structurally and mechanically. These machines have also required elaborate control systems for ensuring proper timing and synchronization of the various manipulations. These machines have thus been undesirably costly, and undesirably complex to maintain and repair.
Many of the automated machines of the above-described type have also required the use of a special preformed blank utilizing corner tabs which project sidewardly through a greater (or lesser) extent than the side flaps in order to ensure that the front and particularly the rear tabs are properly folded. This thus increases the initial cost of the preformed blank since such blanks require substantially more cutting and result in substantial waste. Blanks of this type are also more difficult to handle and manipulate since the projecting corner tabs are more subject to damage. Machines which require such special blanks are disclosed in U.S. Pat. No. 1,868,572 and No. 2,108,334.
While some fold-down box-forming machines have been designed which utilize a conventional blank having corner flaps of the same width as the side flaps, nevertheless the complexities of these machines is even further increased by the necessity of having to provide complex control structure which must be activated and moved in timed relationship with the blank in order to permit proper folding of the rear corner tabs. This control structure greatly increases the cost and maintenance of the machine without significantly increasing the production rate or efficiency of the forming process. A machine of this general type is disclosed in British Specification No. 958,211. As this specification illustrates, movable control fingers are provided and moved in timed relationship with the blank movement so as to effect folding of the rear corner tabs. U.S. Pat. No. 2,125,147 and No. 2,911,889 also disclosure forming machines which require rotatable camlike control members which must be moved in synchronization with the blank to effect folding of the corner tabs.
Another disadvantage of known box-forming machines is that they are normally designed for handling only blanks formed from thin flexible board, specifically paper blanks. These machines, however, have been unable to successfully handle and form boxes from stiff corrugated board in view of the substantial strength and stiffness of same. The folding of corrugated blanks is a much more difficult operation since the blank does not readily flex, so that the only flexing of the blank takes place substantially about the fold lines. The folding structure associated with the known machines has required that the blank itself possess substantial flexibility, such as is present with paper blanks, whereby these machines have been unable to successfully accommodate blanks of corrugated board.
Accordingly, it is an object of the present invention to provide an improved machine for forming knock-down preglued boxes from preformed blanks, which machine overcomes the above-mentioned shortcomings. More particularly, it is an object of the present invention to provide:
1. A forming machine, as aforesaid, which permits the utilization of a standard blank having corner tabs and side flaps of the same width, and which permits the use of a blank formed from stiff corrugated board and permits its efficient formation into a knock-down preglued box.
2. A forming machine, as aforesaid, which provides an improved nonpowered folding structure for automatically folding the front corner tabs, whereby there is no need for associated control structure to synchronize the folding structure with the blank movement.
3. A forming machine, as aforesaid, wherein the folding structure involves simple swingable levers which automatically lift the front tabs upon engagement therewith so that the trailing side flaps automatically pass thereunder while the front tabs are being folded over. These automatically return, due to the urging of gravity, to their initial position upon completion of the folding step so as to be in position to engage the front tabs of the next blank.
4. A forming machine, as aforesaid, which permit preformed blanks to be manually fed into the machine with the rear corner tabs having been manually folded over, whereby the structure and operation of the machine is substantially simplified without significantly effecting the production rate and efficiency of the machine operation.
5. A forming machine, as aforesaid, which is substantially less expensive to both manufacture and maintain, which permits the successful formation of knock-down boxes from stiff blanks of corrugated board, which can be easily and accurately adjusted to accommodate blanks of different size, and which permits an efficient and rapid rate of production while requiring only minimal operation manipulation.
Other objects and purposes of the invention will be apparent to persons familiar with this technology upon reading the following specification and inspecting the accompanying drawings.